1. Field of the Invention
The present invention relates to an active-matrix displaying apparatus in which an organic EL (electroluminescence) device serving as a current control device is used.
2. Description of the Related Art
A voltage-programming pixel circuit which sets an input data voltage according to a gradation to be displayed has been known as a pixel circuit to be used for an active-matrix organic EL displaying apparatus. Incidentally, the pixel circuit like this generally comprises a driving transistor for supplying a current based on the input data voltage to an organic EL device. Here, there is a fact that a threshold voltage varies according to the driving transistor to be used. For this reason, there is a problem that, even if the same input data voltage is set to each pixel circuit, a luminance of the organic EL device varies resultingly. Under the circumstance, Japanese Patent Application Laid-Open No. 2003-271095 discloses, as a method of solving the above problem, a voltage-programming pixel circuit which is able to cancel an influence of variation in a threshold voltage of a driving transistor.
That is, in the pixel circuit disclosed in Japanese Patent Application Laid-Open No. 2003-271095 which comprises two transistors and two capacitors, a capacitance of a parasitic capacitor CL which is connected to a current control device in parallel is made larger than a capacitance of a storage capacitor CS which is connected between the gate electrode and the source electrode of the driving transistor. Consequently, since it is possible to reduce a level of an input video signal, such a constitution is advantageous in terms of consumed power.
However, in such a technique as described above, a large layout area is necessary to form a large-capacity capacitor. Further, since the parasitic capacitor CL is provided for each pixel circuit, a region which is necessary to provide the parasitic capacitor in each pixel circuit becomes large, whereby there is a problem that it is difficult to provide a finer-pitch (more precise) pixel circuit.